X MEnie FIGURE 25.18 Scanning electron micrographs of transverse nent gas-filled spaces (gs) in the cortex(ex), formed by sections through roots of maize, showing changes in struc. degeneration of cells, The stele (all cells interior to the ture with oxygen supply. ( 150x)(A)Control root, supplied endodermis, En)and the epidermis(Ep)remain intact. X, with air, with intact cortical cells. (B)Oxygen-deficient root xylem. Courtesy of ). L. Basq and M C Drew. growing in a nonaerated nutrient solution. Note the promi- Figure 13-7Figure 13-7